[too-mer, tyoo-]
a swollen part; swelling; protuberance.
an uncontrolled, abnormal, circumscribed growth of cells in any animal or plant tissue; neoplasm.
inflated pride; haughtiness.
pompous language; bombast.
Also, especially British, tumour.

1535–45; < Latin: a swelling, swollen state, equivalent to tum(ēre) to swell + -or -or1

tumorlike, adjective
tumorous, tumoral, adjective
antitumor, adjective, noun
antitumoral, adjective
nontumorous, adjective
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
tumour or tumor (ˈtjuːmə)
1.  pathol
 a.  any abnormal swelling
 b.  a mass of tissue formed by a new growth of cells, normally independent of the surrounding structures
2.  obsolete pompous style or language
[C16: from Latin, from tumēre to swell]
tumor or tumor
[C16: from Latin, from tumēre to swell]
'tumorous or tumor
'tumoral or tumor

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin & History

1540s, from L. tumor "swelling, condition of being swollen," from tumere "to swell" (see thigh).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

tumor tu·mor (tōō'mər, tyōō'-)

  1. An abnormal growth of tissue resulting from uncontrolled, progressive multiplication of cells and serving no physiological function; a neoplasm.

  2. A swollen part; a swelling.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
tumor   (t'mər)  Pronunciation Key 
See neoplasm. See Note at cancer.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary

tumor definition

An abnormal mass of new tissue growth that serves no function in the body. Tumors are usually classified as benign or malignant and are often caused by cancer.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
If one cell can incite tumor growth, researchers know that's the cell to target if they want to stop the tumor's growth.
Take a virtual tour into the growth of a tumor and watch how blood vessels help tu.
When tumor cells are transplanted into experimental mice, only the stem cell variety spurs new cancer growth.
They found that the cells initiated and sustained new brain tumor growth in the
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